The killing frost – casualties and survivors

First a bit of background information so that you guys won’t believe that I am completely stupid growing Lophophora and the likes in an unheated greenhouse in Denmark: 1) Most of these plants are “surplus”, i.e. I don’t have room for them anywhere else – lately several plants have been bought specifically for the cold house, though. 2) The greenhouse is located at my summerhouse, left mostly desolate throughout winter, making it difficult to keep it reliably heated. 3) Many cactus species tolerate more frost than is generally assumed; I’m curious which. 4) The winters in Denmark have been rather mild lately, inviting experiments like this.

With this in place I’m ready to recount how the harsh winter, that has just released its cold grip of Denmark, helped me separate the wheat from the chaff (a blatant euphemism for “killing off alarmingly large parts of my collection”). Just to give an understanding of the severity of the winter, the plants saw almost constant frost for more than 10 weeks, with temperatures measured as low as -15 C (5 F) in the area where the plants grow.


Lophophora williamsii var. echinata coming out of winter

Let’s start with one of the success stories. My Trans-Pecos peyote plants are doing quite well, approximately one in eight died and the surviving plants are not too marked by the frost. The plants I'm growing are descending from material originally collected in the Pecos River area, Val Verde County, Texas (JJH 8608293). The Trans-Pecos peyote is the northernmost form of Lophophora williamsii and is also known as Lophophora williamsii var. echinata.


Trans-Pecos peyote surviving the frost

My regular (Mexican and south Texan) Lophophora williamsii plants fared much worse, less than one in ten of the larger plants survived the winter.


One of the few surviving Lophophora williamsii var. williamsii

This corresponds well with Del Weniger’s observations:

[Lophophora williamsii var. echinata] can also survive the much more severe cold of the Big Bend. I have several times had the smaller form from south Texas [L. williamsii var. williamsii] freeze in San Antonio, while this form [L. williamsii var. echinata] growing in the same bed showed no ill effects.

In the future I'll focus more on the extreme northern forms of peyote, i.e. plants grown from material originating from Shafter, Val Verde, Big Bend and other Trans-Pecos, Texas locations. The Cactus Conservation Institute has an informative page on the differences in traits between Lophophora williamsii var. echinata and var. williamsii.


Frost killed Lophophora williamsii, Starr County, Texas

As mentioned the majority of my large “regular” Lophophora williamsii were killed by the frost. But many medium sized seedling plants actually survived while the larger plants (of the same variety) and yearling seedlings succumbed. As this pattern seems to be rather consistent for plants of the same variety, I guess I can’t write all “regular” Lophophora williamsii casualties off to genetics. My theory is that this “size-conditioned” difference in survival must be related to how well the plants were prepared for the winter, which again may be closely related to the surface-area-to-volume ratio of the plant.

The surface-area-to-volume ratio (SA:V) decreases with size, i.e. a large plant will have less surface per unit of volume than a smaller plant. If we use a half sphere as a model for a globular cactus we get a SA:V of 3/r, where r is the radius. Consequently a large plant will need relatively longer time (per unit of volume) to go flaccid and prepare properly for the winter (as all excess water needs to be evaporated through the surface (the epidermis)). Similarly seedlings are more prone to die of drought as an increased SA:V means increased exposure to the environment in general.

To play it safe the coming growing seasons I'll stop watering my large plants well before I let seedlings go drought dormant in preparation for the winter, and in general start winter preparations earlier than I have used to in the past.

I might consider crossing the surviving mature (non Trans-Pecos) plants and name the cultivar Lophophora williamsii 'Borealis' ;-)


Frost killed Leuchtenbergia principis – outside the rain is weeping

My largest Leuchtenbergia principis is dead (pictured above next to a surviving saguaro) while 3 out of 4 of my smaller Leuchtenbergia principis plants (GL 770; Sierra de la Paila) are looking happy.

Ariocarpus has turned out to be an unconditional coldhouse success. I expected my Ariocarpus fissuratus plants to make it safely through the winter as they originate from locations like Fort Stockton, Texas (JM 122) and Crockett County, Texas (SB 403), but I had doubts about my Ariocarpus kotschoubeyanus var. macdowellii plants (SB 100; El Pilar, Coahuila), and had accepted that I would probably loose my Ariocarpus retusus (SB 310; Cuesta la Muralla, Coahuila). Amazingly they all survived the winter in great style almost looking lush and vigorous, like a winter swimmer surfacing with renewed energy after a cold plunge.


Surviving Ariocarpus, Epithelantha, and Leuchtenbergia plants

Epithelantha is another seriously cold tolerant genus. My Epithelantha micromeris var. greggii plants (Cuesta la Muralla, Coahuila, Mexico) all made it; one is seriously damaged, though – it looks like the root is dead while the crown looks fine, so I hope to be able to re-root it. The Epithelantha bokei plants (SB 416; Brewster Co, Texas) also look fine, but due to the extremely dense spination it is hard to say for sure if they are completely undamaged. Strangely the cold has taken the hardest toll on my regular Epithelantha micromeris (SB1327; near Belen, New Mexico) – this variety of E. micromeris is from the northernmost known locality of the species so I had expected the plants to cope better with the frost.


Surviving Obregonia denegrii plants

Last summer I moved a handful of Obregonia denegrii seedlings (VVZ 163; San Vicente, Tamaulipas) to the coldhouse. I really didn’t expect these plants to be cold hardy, but didn’t have room for them anywhere else. Surprisingly approximately two thirds of the plants survived as illustrated in the above picture (the surrounding pots are not empty, each contain a rather large L. williamsii killed by the cold).

Other success stories are Normanbokea valdeziana, Homalocephala texensis, and Mammillaria meiacantha which all made it through the winter without casualties – the Normanbokea plants are even budding. Acharagma roseana is another species that’s shaking off the winter blues and getting ready to bloom – in general Acharagma seems to handle the cold pretty well, even most of my yearling Acharagma aguirreana seedlings survived. Most Escobaria and Echinocereus obviously had minimal problems with the frost.


Frost killed Lophophora williamsii turning to mush

As mentioned above the majority of my larger, regular Lophophora williamsii plants were killed by the frost, but the more tender Lophophora species like Lophophora diffusa and L. fricii are completely eradicated – I’ll probably not experiment further with these species in the coldhouse, the exception maybe being montane varieties of Lophophora fricii.


Dead Lophophora diffusa

Other species that are completely wiped out include Matucana madisoniorum, an unknown Echinopsis hybrid, Ferocactus glucescens (PP 1354), Lithops lesliei (not exactly a cactus, I know ;-), and Harrisia jusbertii. Surprisingly all my Mammillaria grahamii also died – I had expected this species to be more cold hardy.

Most of my saguaro cactus (Carnegiea gigantea) also succumbed to the frost – 4 plants look like they might survive, most of them badly damaged, but it is too early to say.

I need to start building a new collection of grafting stock – all Trichocereus plants that I grew in the coldhouse are dead, including Trichocereus pachanoi, T. peruvianus, Trichocereus 'Tom Juul’s Giant', and a Penis Cactus… they are all gone. Even plants that were well prepared for the winter died, so Trichocereus is definitely not as tolerant to frost as I had expected.


Decomposing Trichocereus plants

To put the death toll into perspective this is the coldest winter in 14 years in Denmark (followed by March, a month with the most extreme temperature fluctuations in 14 years, which were not very becoming to my struggling plants either). The frost set in just before Christmas and only lifted again in the beginning of March. The lowest temperatures measured in the area were as low as -15 C (5 F).


Outdoor temperature in late January

Once in a while short bursts of thaw set in quickly followed by frost (as indicated by the above graph), making the conditions even harder for the plants.


Outdoor temperature in mid February

The temperature measurements come from a semi-professional weather station located approximately 1.5 km (~ one mile) from where I grow my plants, so these temperatures are representative for those that my plants where exposed to.

To end on a positive note I expect the frost to have killed off many pests also (including red spider mites). Also, I got an affirmative confirmation that it is actually possible for peyote to survive rather extreme conditions in an unheated greenhouse in Denmark... and I got plenty of room for new plants ;-)

The killing frost

The fact that the last many winters have been mild in Denmark has made me act with presumption, ignoring several basic rules for growing cacti in freezing conditions. The week before Christmas Denmark was hit by an early cold spell, bringing hard frost that made many of my coldhouse grown plants suffer the consequences of my folly.


Frozen Lophophora williamsii (SB 854; Starr Co, Texas)

The family spent the Christmas holidays in the summerhouse arriving late December 21, the day of the winter solstice. Of course I had to check up on my plants in the coldhouse first thing, but was met by a disheartening sight: The beautiful turgid, dark jade green Lophophora williamsii plants pictured above are frozen solid.


Lophophora williamsii draped in horticultural fleece

The greenhouse walls are covered with curtains and the plants are draped in horticultural fleece to protect them from the cold, still the temperature was measured to slightly less than -7 C (~ 19 F) just next to the plants. The temperature alone shouldn't be a problem as these plants have endured conditions in the coldhouse since 2004 (actually these very plants started my experiments in Lophophora cold hardiness so I'm double sad to loose them), but freezing conditions combined with plants that haven't had the time to go flaccid before subjected to the frost is a deadly cocktail. I'm sad to admit that I watered the above Lophophora williamsii plants along with a couple of Gymnocalyciums and two large pots of 3 year old L. williamsii seedlings very late in the season (late September). To make things worse October and November came with a perpetual overcast sky and constant, high humidity levels, leaving the plants no chance to dry out thoroughly. Finally, to top things off, December brought very early and double digit freezing temperatures (measured in celsius) killing off the plants still bloated with water. I have learned my lesson and will never water any of my coldhouse plants later than the end of August (the exception being very young seedlings that might otherwise succumb to drought).


Thawed Lophophora williamsii (SB 854; Starr Co, Texas)

Come Boxing Day the frost went away, leaving me with thawing plants and the possibility to asses the damage – unfortunately I had to leave for home the day after, so the exact casualty figures will follow in a later post.

The thawed Lophophora williamsii plants pictured above felt soft and slightly mushy to the touch but I didn't have the heart to squish them to see if they were fluid inside.


Thawed Lophophora williamsii seedlings

The two large pots of 3 year old Lophophora williamsii seedlings are gone for sure. Upon thawing the seedlings first felt like small bags of slush ice before the interior turned completely fluid. Subjected to a light pressure the epidermis broke and liquid oozed out, indicating that the cell walls are lacerated by the frost.


Frost killed Lophophora diffusa

Another mistake I made was to move new plants into the coldhouse without leaving them sufficient time to acclimatize properly for the winter – the plants were moved to the coldhouse in late September/early October. On that account I lost 3 large Lophophora diffusa like the one pictured above.

As is evident from the flaccid (and very much alive) L. diffusa pictured below, these plants are able to survive the cold conditions if treated properly. The two plants are from the same batch, are growing under the same conditions (and the pictures were taken the same day). The only difference being that the survivor was given proper time to adjust to its harsh environment.


Alive Lophophora diffusa

I also recently introduced a handful of new Ariocarpus plants to the coldhouse – they had me somewhat worried but seem to cope.


Frost damaged Penis Cactus

My last mistake was to leave a collection of columnar cacti out on the terrace until mid October, exposing them to precipitation and moisture for much longer than what's healthy for plants that must winter in freezing conditions. This has taken its toll on my formerly so erect Penis Cactus - I'm not sure if the plant is completely killed off by the frost but it is certainly damaged. I'm worried for the rest of my Trichocereus collection also; many of the plants felt completely frozen to the touch but are not showing any evident signs of damage yet – time will tell, though.


The lesson I have learned from this experience is to always expect the worst from the weather and prepare accordingly (which should have been evident in the first place!). Even if the last many winters have been mild, I should have known that frost can set in suddenly and quite early in Denmark – instead of being lulled into the assumption that most of the winter would be mild with hard frost arriving late, as the situation has been the last few years. I won't be that careless in the future.

After a couple of mild days the weather reports again predict a period of hard, day- and nighttime, frost extending into the new year.

Update, April 11, 2010
Read more about the casualties and survivors of the frost.

Lophophora diffusa swelling with water, time-lapse video

I'm keeping my plants completely dry during their winter dormancy and consequently they are rather flaccid come spring. The following time-lapse video shows a couple of my larger Lophophora diffusa plants growing turgid after having their first drink of water in several months.



In a fit of thoughtlessness I also watered the Bowiea volubilis visible in the background. This plant also started to expand generating visual “noise” that makes it harder to see exactly what moves when and where. To amend this mistake I inserted the white markers that act as fixpoints showing how much the cactus will have expanded by the time the video ends.

The pictures used for the time-lapse video were taken over a period of 88 hours starting March 6, 2009 in the afternoon through March 10 in the morning. A picture was taken every 15 minuttes giving a total of 352 photos; these are played back at 24 frames per second resulting in a video lasting slightly less than 15 seconds. Another piece of technical trivia is that each second of the time-lapse video corresponds to 6 hours real-time.

The pictures used for the high-definition (1280x720) version of the video above were cropped to obtain the 16:9 aspect ratio. A time-lapse video based on the uncropped and unmanipulated photos (without white markers) is shown below.



The swelling of the plants is not as evident as I had hoped for so I might try doing another “swelling with water” time-lapse video again next year – this time starring some of the plants from my coldhouse (as they are drought dormant for a longer time than my windowsill grown plants). Also the flickering, caused by the shifting light conditions during the day, is a bit disturbing. If I do a video like this again I'll see if I can avoid ambient light completely.

Flowering Lophophora diffusa, time-lapse video

I took the pictures for this time-lapse video of a flowering Lophophora diffusa in early May, 2008. I can't quite remember why I decided to not publish it back then – I was probably disgruntled by the glitches (a couple of seconds into the movie you can see the plant shift a bit, and after 14 seconds there's an abrupt change in focus) and decided I could do better. Anyways, I never got around to doing that and now, after all these flowerless winter months, the small errors don't seem to matter ;-)



The L. diffusa flower opened amazingly fast. The time-lapse video covers a time span of only 45 minutes and is made from 154 still photos taken at intervals of 15 seconds; the photos are played back at a rate of 10 photos per second (the attentive reader will notice that the above numbers don't add up – the focus change 14 seconds into the video indicates a problem that resulted in loosing images for a period of approximately 6 minutes)


Flowering Lophophora diffusa, time-lapse video

The plant was bought just a couple of months prior to these pictures being taken, as described in my post on a Lophophora bargain.

Update - March 28, 2009
You can now watch the flowering Lophophora diffusa in blazing high-definition ;-) I cropped the photos used for the time-lapse video to a size of 1280x720 in order to make the 16x9 HD movie shown below.

Lophophora flower fest

Several of my plants are flowering right now, including many of the large undetermined Lophophora plants I bought earlier this spring. The plants were sold as Lophophora williamsii but body morphology and flower color suggest that many of them are actually Lophophora diffusa. Even though they flower, it is still difficult to determine the species of some of the plants conclusively, so I suspect them to be of hybrid origin. A handful of flower photos are included below.

Lophophora - experiments in cold hardiness, 2008

As mentioned in the previous post on Ariocarpus and Epithelantha I have experimented with coldhouse grown Lophophora since 2004.


Lophophora williamsii (SB 854; Starr Co, Texas), 2004

The Lophophora williamsii (SB 854; Starr Co, Texas) plants from the 2004 batch are still doing great. The plants are growing true to the type with a glaucous bluish-green epidermis. The one on the left flowered last year so I'll soon be able to produce seeds originating from plants that have survived several seasons in an unheated greenhouse. During winter all my Lophophora plants are wrapped in horticultural fleece - both as a protection against the cold but also to keep out hungry pests.


Lophophora plants wrapped in horticultural fleece

Some of the plants needed to be repotted before the upcoming growing season, for example these Lophophora williamsii (SB 854; Starr Co, Texas) plants from the 2005 batch.


Lophophora williamsii (SB 854; Starr Co, Texas), 2005

The plants started from seed in 2005 have grown to 2.5 - 3 cm (~ 1'') in diameter - with a bit of luck they might flower already this summer.


Uprooted Lophophora williamsii (SB 854; Starr Co, Texas), 2005

I never cease to be marveled by how large a fraction of a Lophophora plant that is actually growing underground. The plant pictured below has a crown that is approximately 1 cm high while the massive part of the taproot amounts to 4 times that and the full root system is more than 10 cm long.


Lophophora williamsii (SB 854; Starr Co, Texas) with exposed root, 2005

The past winter was mild - the coldest temperature registered inside the coldhouse was -5C (23F) - so even my Lophophora diffusa and Lophophora decipiens plants have all survived without any signs of damage.


Lophophora diffusa (Higuerillas, Queretaro, Mexico)

The Lophophora decipiens plants are very shriveled and look in dire need of a drink of water. They'll have to wait for a couple of more weeks in order for the weather to warm up.


Shriveled Lophophora decipiens

Last year I grafted a handful of Lophophora williamsii (SB 854; Starr Co, Texas) seedlings on frost hardy Opuntia compressa (Monmouth County, New Jersey) stock. The grafts seem to be doing well and I'll get back with more information on Opuntia grafting when I've done some more experiments.


Lophophora williamsii (SB 854; Starr Co, Texas) grafted on Opuntia compressa stock

Lophophora bargain

When visiting garden centers and flower shops I'm always checking out their cacti and succulents to see if they have any interesting plants. Usually they don't. This Easter my girlfriend and I were browsing a garden center looking for common hollyhock (Alcea rosea) to plant at our summerhouse when I eyed a trayful of Lophophora plants.


Six large Lophophora plants

The plants are quite large, 7.5 - 8 cm (~ 3'') in diameter, and are looking a bit bloated; they don't have the ancient, mature look and feel you would normally expect from plants this size.


Lophophora 7.5 cm in diameter

Despite their youngish appearance the plants are old enough to be sexually active (many have flower remains peering out of the wool).


Lophophora with flower remains

I don't think the garden center exactly knows what they are selling. The plants are mislabeled as "Lophophera williamsii" and when asked the people at the center had no idea where the plants were produced. Maybe that's why the plants are sold dirt cheap at 35 DKK apiece (approximately 7 USD or 4.5 EUR). Anyway, I ended up buying 9 plants and even though they are allegedly Lophophora williamsii I'm pretty convinced there's at least one L. diffusa among my plants.


Root-bound Lophophora cactus

The plants are extremely root-bound and growing in a peat based soil with (what looks like) blackish lava granules in the mix. After carefully removing the plants from their pots they were left to dry for a couple of days before being repotted.

Four of the plants will probably end up in my coldhouse, and I'm planning to dissect one of the plants to study its anatomy. She who must be obeyed is particularly fond of the last idea - she's already bitching about where to find room for all my new plants ;-)

You can see photos of some of the plants flowering in this post.

Habitat photos – Lophophora etc.

A while ago I stumbled upon a handful of great Lophophora habitat photos published on Wikimedia Commons by Kauderwelsch.


Flowering Lophophora diffusa, near Vizarron, Quéretaro, Mexico


Group of Lophophora diffusa near Vizarron, Queretaro, Mexico


Peyote (Lophophora williamsii), Wirikuta near Wadley, San Luis Potosi, Mexico

Kauderwelsch has also made pictures of other cactus species available; a couple of examples are included below.


Ferocactus latispinus, Oaxaca, Mexico


Mammillaria kraehenbuehlii, Oaxaca, Mexico

Unfortunately no new images have been added by Kauderwelsch lately; based on the quality of the photos already contributed I would like to see more of his work.

The photos are published under the terms of the GNU Free Documentation License. The original high resolution copies of the pictures are available here:

• Flowering Lophophora diffusa, near Vizarron, Quéretaro, Mexico
  
• Group of Lophophora diffusa near Vizarron, Queretaro, Mexico
  
• Lophophora williamsii, Wirikuta, near Wadley, San Luis Potosi, Mexico
  
• Ferocactus latispinus, Oaxaca, Mexico
  
• Mammillaria kraehenbuehlii, Oaxaca, Mexico

You can see more of Kauderwelsch's photos in this post.

Rory’s Lophophora collection

Some time ago Rory contacted me to discuss cacti and mycorrhizal associations (an interesting subject that might be brought up in a later post). During our conversations Rory revealed himself as an avid Lophophora grower with an impressive collection of mature and well-grown plants. Rory has kindly allowed me to share some pictures of his plants.


Flowering Lophophora williamsii, close-up


Large pot of Lophophora williamsii

The largest of the L. williamsii plants in this pot are approximately 25 years old. One of the plants in the central group (a bit above and to the left of the center) has been decapitated and set 4 offshoots. One of these has not yet developed a central growing point and appears somewhat cristate, but Rory expects it to develop as normal with time. The removed top was rooted and is also growing in the central group of plants (slightly below center; wool removed from areoles), and is flowering regularly.


Large pot of Lophophora fricii

According to Rory the compost used for the L. fricii plants are not drying fast enough. Consequently the plants are kept on the dry side which accounts for the red coloration shown by some of them. The largest of the plants (with a total of 9 offsets) has only grown 1cm (~0.4'') in the past 9 years so Rory is planning on repotting the plants in a new mix and expects this to speed up growth.


Lophophora diffusa about to flower

The above L. echinata diffusa plant is just about to flower - unfortunately it’s too overcast for the flowers to open properly.


Large pot of Lophophora williamsii v .caespitosa

To top things off (or just to make me completely envious ;-) Rory also threw in a photo of a nice, mature Ariocarpus fissuratus specimen.


Flowering Ariocarpus fissuratus

I hope you enjoyed this “guest appearance” - I for one would like to see more of Rory’s plants. If you have pictures or information you would like to share, you can drop me a mail at “lophophora [dot] blog [at] gmail [dot] com”.

Lophophora and Epithelantha - experiments in cold hardiness II

Since 2004 I’ve experimented with growing Lophophora, Epithelantha, and Acharagma in an unheated greenhouse in Denmark. The winter this year has been damp but not very cold - the coldest temperature registered in the coldhouse was -5C (23F) – so even the L. diffusa plants are doing great.


Lophophora williamsii (SB 854; Starr Co, Texas)

The L. williamsii plants (sown May 2004) are thriving in the coldhouse. The epidermis is glaucous bluish-green, much truer to the type than plants grown in my windowsill. All my cold grown Lophs are wrapped in horticultural fleece during winter – not so much because of the temperature, but to avoid attacks from various critters. This kind of damage is not a problem with the spine covered species.


Lophophora diffusa (Higuerillas, Queretaro, Mexico)

In 2005 I sowed L. diffusa and L. decipiens to grow in the coldhouse. Especially the L. diffusa plants had a hard time last winter and only 2 survived. Both are now doing fine and are developing the typical yellowish-green epidermis.


Lophophora decipiens

L. decipiens is not a “good” species; it’s probably just a cultivar form of Lophophora fricii (I couldn’t obtain any collection data for these seeds either when I bought them). Anyway, the plants are doing well and are getting ready to go 8-ribbed at an age of two.

I’m growing both “regular” Epithelantha micromeres and Epithelantha micromeris v. gregii. The gregii variety seems to be a faster grower than the regular micromeres; it also has a very beautiful coverage of spines, as illustrated below.


Epithelantha micromeris v. greggii (Cuesta la Muralla, Coahuila, Mexico)


Epithelantha micromeris v. greggii – closeup

All of the Epithelantha plants made it through this winter without damage.